ZHCSN08D August 2020 – April 2024 DRV8714-Q1 , DRV8718-Q1
PRODMIX
It should be ensured that the charge pump load capability is sufficient for the type of external MOSFET, number of PWM half-bridges, and desired PWM frequency. This can be confirmed with a simple calculation as shown in Equation 1. Since the charge pump supplies both the high-side and low-side gate drivers, the number of both switching high-side and low-side MOSFETs should be taken into consideration. This will depend on both the number of PWM half-bridges and the freewheeling mode (if the opposite MOSFET is being switched).
Using the input design parameters as an example, we can show that in this scenario that output load capability of the charge pump is sufficient in Equation 2. For this example, four active half-bridges were assumed with active freewheeling totaling 8 switching MOSFETs.